ASUS BIOS archive for the X542UN, with 2.0 in the name, which most likely refers to the mainboard revision rather than a firmware version. The 5.4 MB RAR should be extracted and its image size compared with the SPI flash on the board before programming. ASUS laptops store serial number, UUID and sometimes the Windows key in the BIOS region, so read and save the original chip first and transfer that data if needed. Confirm the model and board revision printed on the PCB match before writing with a programmer.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @biosarchive. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →